Uterine blood flow and nutrient uptake during late gestation in ewes with different number of fetuses.

Twenty-three unanesthetized ewes with, single, twin or triplet lambs and with indwelling femoral artery and utero-ovarian vein catheters were studied at 105 or 121 days of gestation, Glucose and a-amino acid nitrogen (a-NH 2-N) uptake by the gravid uterus was determined from arterial-venous (A-V) differences and utero-ovarian blood flow measurements. Uterine blood flow was determined by p-aminohippuric acid (PAH) dilution and radioactive microspheres methods and results from the two methods in eight animals were highly correlated (r -.93; P<.01). Arterial blood flow (microsphere method) to the gravid uterus was greater than utero-ovarian vein blood flow (PAH method) by a factor of 1.33. Utero-ovarian vein blood flow in ewes with twin fetuses at 105 days of gestation was 958 +164 ml/min and was approximately 406 ml/min greater (P<.I) in ewes with triplets at the same stage of gestation. Utero-ovarian vein blood flow increased (P<.I) 400 ml/min as stage of gestation increased from 105 to 121 days of gestation for ewes with twins. Total glucose and a-NH2-N uptake (mg/min) tended to increase with stage of gestation and tended to be greater